1. Field of Invention
This invention relates to a film-forming dispersion useful for formation of a protective coating on shaped drug and food articles. In particular, this invention relates to a film-forming dispersion containing essentially acetylester of oxidized starch and triethylcitrate useful for surface protection of drug and food containing tablets, pellets, pills, granules or their components in crystalline form, especially those containing one or more active substances and ingredients.
2. Background Art and Related Art Disclosures
It is generally known that the drugs, medicaments, food supplements or food substitutes intended for oral administration, when molded into the final form, are often sensitive to physical and chemical effects of the environment, such as heat, light or humidity, all of which substantially decrease the shelf-life of the preparation. Moreover, many of these preparations have an unpleasant flavor properties. Also, in case of more than one active ingredient, undesirable chemical reactions may occur among the active components themselves or between an active component and an auxiliary component. For these reasons the final product or some of its active components should be protected by coating these components with protective films (layers) which would provide a barrier preventing detrimental inter-reactions between various components or decomposition of active ingredients by heat, light, humidity, etc. Such protection is usually achieved by coating these articles or components with solutions of various film-forming substances.
The oldest known method for surface protection of tablets, pellets, pills, granules, etc., is the pelletization where the surface of molded drug cores (uncoated tablets, pills, etc.) is covered with a thick layer of saccharose optionally containing also other auxiliary compounds including dyes.
Another type of surface protected drugs are so called core coated tablets whose active ingredient containing core is coated either with a thin layer of a cellulose derivative or with a suitable polymeric material. Most commonly used coating materials are cellulose derivative hydroxypropyl methylcellulose, and polymers acrylates and methacrylates. All of these film-forming solutions used for the core coating, however, are based on the presence of organic solvents or their mixtures. The protective film is formed on cores after the solvent evaporation, releasing said solvent into the atmosphere. Besides the environmental pollution, there is also a large loss of the organic solvents which has an economic impact. Further, the handling of organic solvents may endanger workers' health and is fire hazardous. However, for lack of better coating process, the method is widely used and effective equipments have been developed to produce these protective films containing hydropropyl methylcellulose and polymers in large quantities.
The primary disadvantage of these above described method of preparation of surface protected articles is the fact that the film-forming substances are soluble only in solutions containing organic solvents or their mixtures, both of which may leave residues in the article coating or be otherwise harmful to the patient or consumer. Thus, it would be extremely advantageous to have available coating which would allow the elimination of the use of organic solvents or their mixtures.
Previously, certain attempts were made to exclude from the technology of preparation of surface protected articles the film-forming solutions based on organic solvents and replace them by water based solutions or dispersions. For this purpose, some water-soluble cellulose derivatives, such as hydroxypropyl methylcellulose, commercially available from DOW Chemical as Methocel E5 and E15 or water dispersions of acrylate polymers, commercially available as Eudragit.TM. from RHOM PHARMA, Germany, were developed. The water cellulose, however, form very viscous solutions and therefore are not overly suitable for achieving the effective coating.
While possessing much better properties than organic solvents coatings, these film-forming water solutions and dispersions are not without shortcomings. For example, the disadvantage of hydroxypropyl methylcellulose used frequently for these dispersions is its viscosity. Because it forms rather viscous solutions, it can only be used in a concentration of up to 8%. The disadvantage of the water dispersions of the acrylate polymers, on the other hand, is their instability towards external effects of temperature, pressure and their incompatibility with other auxiliary compounds. Since it is not easy to rapidly remove the water from the water based film-forming solutions, the cores containing active ingredient are for a relatively long period of time in contact with water while being, at the same time, submitted to high temperatures and continuous aeration. This is especially so when working in fluid bed. Under these circumstances, the decomposition of the active substances can and does easily occur.
It would be, therefore, advantageous to have available a coating method which would avoid such long exposure of the active ingredient to the water, aeration, and high temperature and still achieve the same purpose, that is a long-term protection of the active ingredient containing core against excessive heat, humidity or light deterioration.
It is, therefore, a primary object of this invention to provide a film-forming dispersion which would effectively protect core containing active ingredient without submitting the core to undesirable contact with water for extended period of time as well as to high temperature, pressure, and aeration The current invention concerning a novel type of protective coating avoids all these undesirable exposures while resulting in effective, desirable, safe and economical protective coating for drug and food containing articles and objects.